sph_src += files(
    'density_summation.f90',
    'navier_stokes_solver.f90',
    'smoothed_kernel_function.f90',
    'external-force/external_force.f90',
    'internal-force/internal_force.f90',
    'internal-force/EoS.f90',
    'internal-force/artificial_force.f90',
    'linked_list_nnps.f90',
    'leap_frog.f90',
)
